Surface modification of cellulose nanocrystal and its applications in flame retardant epoxy resin

Advances in the Study of Flame-Retardant Cellulose and Its Application in Polymers: A Review

Cellulose, as a green and renewable polymer material, has attracted the attention of a wide range of scholars for its excellent mechanical strength, easy chemical modification and degradability. However, its flammability limits its application in automotive, aerospace, construction, textile and electronic fields. This review recapitulates the modification methods of flame-retardant cellulose and their applications in polymers in recent years. This paper discusses the fabrication of flame-retardant cellulose from various aspects such as boron, nitrogen, phosphorus, sulphur, inorganic and heterogeneous synergistic modification, respectively, and evaluates the flame retardancy of flame-retardant cellulose by means of thermogravimetry, cone calorimetry, limiting oxygen index, the vertical combustion of UL94, etc. Finally, it discusses the application of flame-retardant cellulose in actual composites, which fully reflects the extraordinary potential of flame-retardant cellulose for applications in polymers. Currently, flame-retardant cellulose has significantly improved its flame-retardant properties through multi-faceted modification strategies and has shown a broad application prospect in composite materials. However, interfacial compatibility, environmental protection and process optimisation are still the key directions for future research, and efficient, low-toxic and industrialised flame-retardant cellulose materials need to be realised through innovative design.

Accessible preparation of a novel nitrogen‑phosphorus synergetic nanocellulose-based flame retardant with excellent char-forming ability for enhancing the anti-melting droplet property of PA66

Developing eco-friendly and effective flame retardants is crucial for enhancing the fire resistance of polymeric materials. This study developed a novel nitrogen‑phosphorus (NP) synergistic nanocellulose-based flame retardant (CNC-PEI-PA) by grafting polyethyleneimine (PEI) and phytic acid (PA) onto the CNC. CNC-PEI-PA demonstrated remarkable thermal stability, char-forming ability, and antibacterial activity. Notably, the height of the intumescent char layer for CNC-PEI-PA increased by 700 %, and the char yield improved from 24.5 % to 45.0 % compared to CNC. Introducing CNC-PEI-PA into polyamide 66 (PA66) raised its maximum decomposition temperature to 470.0 °C and increased the char yield by nearly 330 %. More importantly, the quick formation of a dense intumescent char layer functioned as a robust protective barrier, enhancing the flame retardancy of PA66 while also greatly improving its anti-melting droplet property. The successful preparation of NP synergistic bio-based flame retardants through a facile and eco-friendly synthetic route shows their significant potential to enhance both the flame retardancy and anti-melting droplet properties of polymer materials.

Enhancing flame retardancy, antibacterial activity and UV resistance of polyamide 66 fabric by fully biobased intumescent flame-retardant nanocellulose coating

Polyamide 66 (PA66) fabric, one of the most common textile materials, presents great fire hazards to human safety and property due to its intrinsic flammability. In this study, fully biobased intumescent flame-retardants (IFRs) composed of cellulose nanocrystals (CNC), tannic acid (TA) and phytic acid (PA) were synthesized and coated onto the surface of the PA66 fabric for improving the flame retardancy, antibacterial and UV resistance. It is found that IFR coating effectively suppressed the droplet and smoke phenomenon of PA66 fabric, and the total smoke production (TSP) and smoke production rate (SPR) values of the fabric were significantly reduced by 71.0 % and 36.7 %, respectively. The synergistic effect of condensed phase and gas phase flame retardancy could be responsible for the remarkable improvement in the flame-retardant property of the treated PA66 fabric (PA66/IFR). Owing to the TA in the IFR coating, PA66/IFR3 fabric showed obvious antibacterial activity and UV resistance. Furthermore, the PA66/IFR3 fabric retained adequate mechanical properties and maintains satisfactory air permeability. This study provides a green and convenient solution for developing multifunctional PA66 fabrics to meet diversified demands.

Enhancing flame retardancy and heat insulation performances of polyamide 66 composite film by adding CNC/Al2O3 nanohybrids

Polyamide 66 (PA66) has garnered significant attention due to its exceptional properties; unfortunately, its flammability is challenging. Adding flame retardants (FRs) is a primary approach to enhance PA66 flame retardancy. This study developed a highly flame-retardant PA66 composite film by adding corn-like functional nanohybrids (CNC/Al2O3). Interestingly, CNC/Al2O3 nanohybrids not only formed hydrogen bond interactions with PA66 but also improved crystallization properties as heterogeneous nucleating agents, resulting in the excellent mechanical properties of PA66 composite film. Remarkably, the incorporation of 3 wt% CNC/Al2O3 nanohybrids into PA66 matrix contributed to increasing the LOI to 28.5 %. The pHRR, THR, and TSR were reduced obviously by 55.7 %, 15.3 %, and 65.2 %, respectively. The excellent flame retardancy of PA66 composite film was attributed to the forming of a compact carbon layer catalyzed by the CNC/Al2O3 nanohybrids. Besides, the homogeneous distribution of CNC/Al2O3 nanohybrids endowed the composite film with excellent heat insulation, and the heat insulation rate was up to 31.9 %. Thus, such PA66 composite films with excellent flame retardancy, heat insulation, and mechanical properties could meet the broader application requirements.